A three-dimensional polydimethylsiloxane (PDMS)-based microarray was one-step fabricated by releasing from an SU-8 mold for cell trapping. A human embryonic kidney-293 cell line was cultured on the PDMS microarray. By taking advantage of the chemical nature difference between PDMS surface released from oxidized silicon and released from SU-8 substrate, cells can only grow and be attached inside the PDMS microarray after 2 days of cell culture. To investigate the substantial nature of the cell adhesion and repellency on the PDMS substrate, atomic force microscopy, contact angle, and x-ray photoelectron spectroscopy methods have been carried out to analyze the physical and chemical properties of the PDMS material surfaces under different surface treatment circumstances.

We designed, fabricated and characterized MEMS-enabled mechanically-tunable photonic crystal lens comprised of 2D
photonic crystal and symmetrical electro-thermal actuators. The 2D photonic crystal was made of a honeycomb-lattice of
340 nm thick, 260 nm diameter high-index silicon rods embedded in low-index 10 &mu;m thick SU-8 cladding. Silicon input
waveguide and deflection block were also fabricated for light in-coupling and monitoring of focused spot size,
respectively. When actuated, the electro-thermal actuators induced mechanical strain which changed the lattice constant
of the photonic crystal and consequently modified the photonic band structure. This in turn modified the focal-length of
the photonic crystal lens. The fabricated device was characterized using a tunable laser (1400~1602 nm) and an infrared
camera during actuation. At the wavelength of 1450 nm, the lateral light spot size observed at the deflection block
gradually decreased 40%, as applied current increased from 0 to 0.7 A, indicating changes in focal length in response to
the mechanical stretching.

We report the development of a high efficiency magnetic microfluidic mixer based on a novel 3D impellor-shaped ferromagnetic micro-stirrer bar. The 3D impellor-shaped micro-stirrer bar with 31.6º inclined angle is fabricated using titled (55º) SU-8 exposure technique. The 3-D inclined micro-stirrer bar causes 3-D perturbation of fluids resulting in rapid mixing in microscale. When compared with a vertical straight sidewall micro-stirrer bar, approximately 20% of mixing efficiency enhancement is achieved.

In this paper, we present the design, fabrication and characterization of an inductively-coupled miniaturized RFID transponder using MEMS technology. The micromachined miniaturized transponder consists of a small solenoid inductor with a high permeability magnetic core, a chip capacitor and a RFID chip. They are integrated onto a micromachined SU-8 polymer substrate and it is operated in the frequency range of 13.56 to 27 MHz. Induced voltages of up to 4 V were obtained with a miniaturized 500 nH transponder coil from a 2.2 &#956;H reader coil at 5 mm distance based on a resonant magnetic coupling mechanism. The assembled transponder was tested using a commercial RFID reader at 13.56 MHz and successful communication was established at a distance of 10 mm.

We show experimental results of anomalous refraction through a photonic crystal membrane. The membrane layer consists of a thin polymer film suspending a triangular array of silicon pillars. Light is coupled into the photonic crystal (PC) through ridge waveguides etched onto a silicon substrate. By altering the shape of the tip of the input waveguides, we can shape the light that is incident into the PC. In this paper we show that when we shape the field to be quasi point source like, the PC focuses the incident light onto a deflection block placed behind the membrane structure. We experimentally observe focusing of both TE and TM light inside the PC. In the same structure we have previously shown that when we illuminate the PC with a much broader beam incident at an angle, the light negatively refracts through the crystal. We designed the device so that it is capable of being stretched by mechanical actuators, which will stretch the polymer film and silicon lattice and distort the photonic band structure. Mechanical stretching of the dimensions of the flexible PC makes possible a device that can dynamically change its beam steering and focusing properties.

We report data on a new nanophotonic device based on a 2-D slab silicon photonic crystal (PC) matrix composed of a periodic array of high index silicon pillars embedded within a flexible low index polyimide matrix. To our knowledge, for the first time, negative refraction based on the superprism effect is reported in a 2-D silicon-based photonic crystal device. This work has a huge potential in various applications employed within silicon-based photonic crystal systems such as super-lenses, tunable filters, and optical switches.
The device, designed for 1.54 &#956;m infrared light, is composed of a triangular array of silicon pillars of diameter 400 nm with a lattice spacing of 616 nm embedded in a thin 400 nm thick polyimide matrix. Small changes in the incoming angle of light can produce large changes in the direction of the outgoing light near zero stress.
Silicon pillars are formed by RIE etching and polyimide is then spun on, baked and etched to form the PC device. The PC matrix is then released from the oxide with a BOE etch. Samples with incident angles in the range of 0° ~ 8° have been tested. Strong negative refraction on the order of 50° is seen in the PC with the incident angle of 8°. This is in close agreement with the simulated results and clearly demonstrates the effectiveness of the photonic crystal device.

The emergence of vertical cavity surface emitting laser (VCSEL) and photo diode (PD) arrays has given scope for the development of many applications such as high speed data communication. Further increase in performance can be obtained by the inclusion of micro-mirrors and microlens in the optical path between these components. However, the lack of efficient assembly and alignment techniques has become bottlenecks for new products. In this paper, we present development of optical sub-assembly and metallic MEMS structures that enable in the massively parallel assembly and alignment of these components to form a single miniature package. VCSEL wafer was processed to have polymer pedestal and polymeric lens on top of it. Such optical sub assembly greatly increases coupling efficiency between the VCSEL and optical fibers. Multiple numbers of suspended MEMS serpentine springs made out of electroplated nickel have been fabricated on ceramic substrates. These springs serve for clamping and alignment of multiple numbers of optoelectronic components. They are designed to be self-aligning with alignment accuracies of less than 3 micron after final assembly. Electrical connection between the bond pads of VCSEL's and PD's to the electrical leads on the substrate has been demonstrated by molten solder inkjet printing into precisely designed MEMS mold structures. This novel massively parallel assembly process is substrate independent and relatively simple process. This technique will provide reliable assembly of optoelectronic components and miniature optical systems in low cost mass production manner.

We report a tunable nanophotonic device concept based on flexible photonic crystal, which is comprised of a periodic array of high index dielectric material and a low index flexible polymer. Tunability is achieved by applying mechanical force with nano-/micro-electron-mechanical system actuators. The mechanical stress induces changes in the periodicity of the photonic crystal and consequently modifies the photonic band structure. To demonstrate the concept, we theoretically investigated the effect of mechanical stress on the anomalous refraction behavior and observed a very wide tunability in the beam propagation direction. Extensive experimental studies on fabrication and characterizations of the flexible photonic crystal structures were also carried out. High quality nanostructures were fabricated by e-beam lithography. Efficient coupling of laser beam and negative refraction in the flexible PC structures have been demonstrated. The new concept of tunable nanophotonic device provides a means to achieve real-time, dynamic control of photonic band structure and will thus expand the utility of photonic crystal structures in advanced nanophotonic systems.

We present the design, fabrication, and characterization of surface micromachined on-chip 3-D air-core arch-shape solenoid microinductors. Combinations of unique surface micromachining fabrication process techniques, such as deformation of polymeric sacrifical molds and conformal electrodeposition of photoresist molds on nonplanar sacrificial polymer mounds, are utilized. An air gap inserted between the inductor's body and the substrate is used to reduce the degradations of high-frequency inductor performances. Fabricated inductors are characterized and modeled at high frequencies from S-parameter measurements. ABCD parameters, derived from measured S parameters, are translated into a simplified physical π model. The resulting 2-, 3-, and 5-turn arch-shape suspended air-core solenoid inductors have inductances between 0.62 to 0.79 nH, peak quality (Q) factors between 15.42 to 17 at peak-Q frequencies between 4.7 to 7.0 GHz, and self-resonant frequencies between 47.6 to 88.6 GHz.

Electron beam lithography (EBL) is widely used for patterning of sub-micron and nano-scale patterns. Patterns in the order of tens of nano meters have been successfully realized using EBL. There are increasing needs in high aspect ratio structures in sub-micron and nano scales for microelectronics and other applications. Traditionally, high aspect ratio structures in sub-micron and nano scales have been realized by precision lithography techniques and subsequent dry etch techniques. In this work, we present commercially available SU-8 as a potential resist that can be used for direct resist patterning of high aspect ratio structures in sub-micron and nano scales. Such resist pattern can be used as a polymeric mold to create high aspect ratio metallic sub-micron and nano scales structures using electroplating technology. Compared to the most commonly used EBL resist, PMMA (poly methylmethacrylate), SU-8 requires a factor of 100~150 less exposure doses for equal thickness. It results in a significant reduction of EBL processing time. In this paper, characterization results on the patterning of up to 4:1 aspect ratio SU-8 structures with minimum feature size of 500 nm is reported. In addition, preliminary results on high aspect ratio metallic sub-micron structures using electroplating technology are also reported.

It is of great interest to develop an efficient and reliable manufacturing approach that allows for the integration of microdevices each of which is optimally fabricated using a different process. We present a new method to achieve electrical and mechanical interconnects for use in heterogeneous integration. This method combines metal reflow and a self-aligned, 3-D microassembly approach. The results obtained so far include a self-aligned, 3-D assembly of MEMS to MEMS, post-processing which selectively deposited indium on 50 &mu;m-thick MEMS structures, and reflow tests of indium-on-gold samples demonstrating 15-45 m&Omega; resistances for contact areas ranging from 100 to 625 &mu;m<sup>2</sup>. 3-D microassembly coupled with metal reflow allows for the batch processing of a large number of heterogeneous devices into one system without sacrificing performance. In addition, its 3-D nature adds a new degree of freedom in system design space. Downward scalability of the method is also discussed.

This work reports a new approach to fabricate spiral on-chip inductors with suspended dome-shape metal tracks. The new fabrication techniques are aimed at reduction of substrate losses by fabrication of spiral metal tracks on top of a sacrificial polymeric dome so that the inductor is suspended in the air when the dome is finally removed. In addition, the reduction of fringing capacitance between the spiral metal tracks is expected since the tracks sidewalls are not fully overlap to each other. Dome-shape spiral inductors made of copper were demonstrated. Currently, high-frequency characterizations of these inductors are under way.

This paper presents a rapid replication technique for polydimethylsiloxane (PDMS) high aspect ratio microstructures (HARMs) and a pattern transfer technique for replication of metallic HARMs on other substrates (such as circuit containing substrates) using such replicated PDMS HARMs. A high aspect ratio metallic micromold insert, featuring a variety of test microstructures made of electroplated nickel, has been fabricated by the standard deep X-ray lithography (DXRL) process. Mixed pre-polymer PDMS with a curing agent has been cast onto the metallic micromold insert test patterns to create replicated polymeric HARMs. The replicated PDMS HARMs could be used to massively reproduce high aspect ratio metallic microstructures on other substrates using a pattern transfer technique. In order to demonstrate the concept, an experiment has been carried out to attach the replicated PDMS HARMs onto a silicon substrate which has pre-deposited photoresist and metallic seed layer. Electrodeposition has been carried out through the attached PDMS HARMs mold followed by the subsequent removal of the PDMS, resulting in high aspect ratio metallic microstructures on the silicon substrate. This technique could be used to massively reproduce metallic HARMs on circuit containing substrates to create 3-D integrated MEMS devices.

A novel on-chip 3D air core micro-inductor, utilizing deformation of sacrificial thick polymer and conformal photoresist electrodeposition techniques, is reported. The bottom conductors are formed on silicon or glass substrate by metal electroplating through SU-8 polymeric mold. A thick SJR 5740 photoresist is then spun on and patterned to be a supporting mesa. Hard curing of such polymer mesa could significantly deform it into a cross-sectional bell-shape sacrificial core with graded profile in which is used to support top conductors formation. A layer of conformal electrodeposited photoresist (PEPR 2400) is then coated along the core's surface profile, patterned by standard optical lithography and filled up by metal electroplating. Finally, all polymeric molds including significantly deformed sacrificial core and electroplating bases are removed, resulting in an on-chip solenoid-type 3D air core micro-inductor. Since this new inductor has an air core and has only two contact points per turn, the core loss and equivalent series resistance are expected to be small, and hence, to give higher quality factor at high-frequency operation. Currently, high-frequency characterization of this on-chip inductor is under way.

The use of amorphous silicon solar cell array high voltage power source as an on-demand wireless power source for electrostatically actuated 32 X 32 micromirror array is presented. The amorphous silicon solar cell array has been reported previously by authors of this paper. In this work, the solar cell array has been used to drive distributed electrostatic actuator array (micromirror array in this particular paper). A 32 X 32 micromirror array has been fabricated and the size of single micromirror is 200 micrometer X 200 micrometer. Static deflection test of micromirrors has been carried out and pull-in voltage of 44 V and releasing voltage of 30 V was found. The electrical output of the solar cell array has been directly connected to the 32 X 32 micromirror array to demonstrate a wireless powered distributed MEMS actuator array. A total solar cell array area of 0.3 cm<SUP>2</SUP> (30 series-interconnected solar cells) were used to drive a part of 32 X 32 micromirror array (a total array area of 0.4 cm<SUP>2</SUP>). Motion of multiple numbers of micromirrors was reproducibly observed. The ultimate goal of this research is to achieve power-integrated autonomous MEMS using solar cell array as a miniaturized wireless on-board power source and distributed actuator array as a locomotive engine.

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Journal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews